Scientists Set a New Distance Record for Quantum Teleportation

We're another step closer to an "unhackable" internet.

Scientists have teleported the quantum state of a light particle over six kilometers (roughly 3.7 miles), setting a new distance record for quantum teleportation—and taking another step towards creating an internet that's secure from hacking threats, including those posed by future quantum computers.

The challenge here is that so much of our communications—whether banking transactions, personal health information, or classified government files, to name a few examples—rely on cryptographic tools that quantum computers, once they become available, will be able to crack. Current cybersecurity attacks "exploit things like faulty implementation, or an insider threat," Michele Mosca, co-founder of the Institute for Quantum Computing at the University of Waterloo, told me. "They can be very costly, but when they're detected, you can fix it."

Wolfgang Tittel (right) and his team. Image: Riley Brandt, University of Calgary

Cryptographic tools "generally rely on some math problem being hard," Mosca continued. What might be difficult or impossible for a classical computer to solve—for example, factoring a very large number into primes—will not necessarily challenge a quantum machine.

Of course, nobody knows for sure when the first true quantum computer will be available, although it's getting closer. Mosca authored a recent report estimating a one-in-seven risk that, within a decade, emerging quantum technologies will undermine some of the most important public key cryptography systems, which are widely used today to protect data online—and a 50 percent chance that many of them will be obsolete by 2031.

Once a nation-state (or eventually a well-funded criminal group) gets its hands on a quantum computer, "we're not talking about a patch-up job," said Mosca, who is presenting at a conference this week in Toronto that addresses the future quantum threat to businesses and governments. "When your foundations are broken, there's no way to fix it."

Which brings us back to quantum teleportation. According to physicist Wolfgang Tittel of the University of Calgary, quantum cryptography could keep communications safe. Although the verdict is still out on many other systems, "we know for sure that quantum key distribution is not vulnerable to a quantum computer," Tittel told me. He is lead author of a new study, published alongside a similar demonstration from a Chinese team, in Nature Photonics.

The teleportation experiment relied on what Einstein famously called "spooky action at a distance"—quantum entanglement, which means that two particles share certain properties even over large distances. Here, scientists temporarily took over part of the city of Calgary's fiber optic cable network to send the signal.

Scientists teleported the quantum state of a particle of light over six kilometers. Image: Riley Brandt, University of Calgary

It's not that an entire photon (or light particle) was sent via the cable, Tittel emphasized. "The transfer happens in a disembodied manner," he explained. "The state [of the particle] appears on the receiver side, without the particle travelling."

Part of the magic of quantum mechanics is that, when a system is directly observed, it collapses. "There's no way to observe it without changing it," he said. "The receiver would see, and know it's been tampered with." That makes for a great guarantee that there are no eavesdroppers on the line, but it also presents a challenge for transmitting communications over distances greater than 200 kilometers, Tittel said.

He and others are trying to get around it by designing quantum repeaters, which would be similar to those that are used in current communications to carry messages over long distances, but ones that are quantum-friendly. "A real quantum repeater will require teleportation and quantum memory," like a hard disk that stores information, Tittel said. "We did the teleportation part," and he hopes to make an advance on quantum memory soon.

Tittel's goal is to "build a quantum network for quantum key distribution" across Calgary, then Alberta, then all of Canada, he told me, "and to [eventually] connect to quantum computers, which I believe will be available in ten-to-twenty years."

Waterloo, where Mosca is based, has earned a reputation as Quantum Valley. When we spoke, Mosca emphasized that quantum technologies hold immense promise, but that we still need to prepare ourselves for their arrival—which means strengthening our cybersecurity systems now.

"We have to make sure we can continue to communicate in secrecy," Tittel said.